Osteoarthritis is the most common musculoskeletal and joint diseases in the world. Because medical advances have increased the average lifespan, yet have not devised an effective means of preventing wear and tear of the joints, osteoarthritis is rapidly becoming a significant medical and financial burden to the world (Pelletier et al. 2006) and is a leading cause of impaired mobility in the elderly. (Felson 2006). Osteoarthritis is a condition of primary failure of articular cartilage, which is accompanied by subchondral hardening of bone, osteophytes (bone spurs) at the joint margin, juxtaarticular bone cysts, and joint space narrowing. Pain is the most prominent and disabling symptom of osteoarthritis. (Felson 2005). Osteoarthritis usually develops in the smaller joints of the fingers, the weight-bearing joints of the leg, and the movable portions of the spine, although any diarthrodial joint can be affected.
Osteoarthritis was long thought to reflect the aging process, in which repetitive use of joints results in cartilage erosion. And whereas it is true that osteoarthritis is characterized by cartilage loss, cartilage damage cannot be the source of the pain, as there are no pain fibers in articular cartilage, and in some patients cartilage loss may occur without any accompanying symptoms. (Felson 2005). As more is understood about the molecular structure and function of cartilage, the pain associated with osteoarthritis appears to be the result of a complex interplay between mechanical, cellular, and biochemical forces.
At present, there are no means to effectively restore damaged articular cartilage to its healthy state, i.e., once damaged, human adult cartilage remains damaged for life. Thus, the primary goals of treatment of osteoarthritis are to help patients understand their disease, relieve their pain, minimize their disability, and limit the progression of their disease. Medical treatment of osteoarthritis often involves administration of pain relievers such as acetaminophen or aspirin. Alternatively, nonsteriodal anti-inflammatory drugs (NSAIDs), such as ibuprofen, nabumetone or naproxen, amongst others, may be administered. Although these drugs act to “block” the pain and/or reduce inflammation, they do not affect the physiology underscoring and producing the pain. Such an approach is suggested by the instant invention.
Articular cartilage itself is relatively avascular, and lacks pain receptors. Thus, although osteoarthritis represents a failure of cartilage, the pain cannot and does not originate from the damaged cartilage itself. Rather, the pain can be mediated by the only peri-articular structures which possess the neural apparatus for sensing pain (i.e., nociceptors): namely, the synovium and the bone underlying the cartilage. It is only those structures (alone or in combination) that can be responsible for the sensation of pain experienced by patients suffering from osteoarthritis.
There is clinical evidence suggesting that pressure within the bone may contribute, at least in part, to joint pain. For example, the medical literature has discussed a case in which Dr. Scott Dye of San Francisco injected his own bone with saline under pressure, in the name of science. He experienced pain which lasted for a year.
Also, more than 30 years ago, it was observed that pain due to severe osteoarthritis may be associated with “intraosseous hypertension,” i.e., pressure within the bone. (Arnoldi et al. 1975). Intraosseous hypertension is the manifestation of edema within the bone. Thus, it has been proposed that local vascular changes may be important in the pathogenesis of degenerative arthritis and the production of its associated symptoms. (Arnoldi et al. 1972). It has been further observed that surgical decompression of bone (specifically in the case of osteonecrosis) can relieve bone pain. Use of surgery, however, to alleviate pressure within the bone is not ideal. For one thing, surgery can produce myriad side effects and complications, but more to the point, the problem with surgical decompression is that its benefit will be transient. The fenestrations created during so-called decompressive procedures are bound to fill with fibrocartilage. Thus, there is an ongoing need for a safe and effective method for alleviating pressure in bone causing joint pain, most typically found in patients suffering from osteoarthritis.